Recently, for example, a liquid crystal display device has been used widely in a liquid crystal television, a monitor, a mobile telephone and the like, as a flat panel display having advantages such as thinness and light-weight in comparison with conventional Braun tubes. Such a liquid crystal display device includes a lighting device (backlight) that emits light and a liquid crystal panel that displays a desired image by playing a role as a shutter with respect to light from a light source provided in the lighting device.
The lighting device is classified roughly into a direct type and an edge-light type depending on the arrangement of the light source with respect to the liquid crystal panel as an object to be irradiated with light. For example, a liquid crystal display device for use in mobile equipment such as a mobile phone, a notebook PC, and a PDA generally adopts the edge-light type, which achieves a smaller thickness more easily than the direct type. More specifically, the edge-light type lighting device includes the light source on a side of the liquid crystal panel for achieving a smaller thickness, and uses a light-guiding plate that has a light emitting surface arranged opposite to a non-display surface of the liquid crystal panel so as to irradiate the liquid crystal panel with light from the light source.
Further, in the conventional lighting device, as described in JP 2007-250458 A below, for example, an opening is formed in a light-guiding plate and a light-emitting diode as a light source is inserted in the opening. Further, it is proposed in this conventional lighting device that, in upper and lower surfaces of the insertion portion of the light-emitting diode of the light-guiding plate, an inclined surface is formed so that the thickness of the light-guiding plate becomes smaller toward an LED substrate (light source substrate) side on which the light-emitting diode is mounted. Further, this conventional lighting device facilitates total reflection of light from the light-emitting diode in the light-guiding plate, thereby enhancing light use efficiency of the light-emitting diode.